Flexible polypropylene resin

ABSTRACT

The present invention relates to a soft polypropylene resin having a melt index falling in a specific range, prepared by melting and kneading a substantial propylene homopolymer or a propylene copolymer composition each having specific properties in the presence of a radical-generating agent. 
     According to the present invention, capable of being provided at a good productivity is a soft polypropylene resin which is useful as an alternative for a polyvinyl chloride resin in the fields of films, sheets, construction materials and the like and which is excellent in fluidity.

BACKGROUND OF THE INVENTION

The present invention relates to a soft polypropylene resin, morespecifically to a soft polypropylene resin which is useful as analternative to a polyvinyl chloride resin in the fields of films,sheets, construction materials and the like and which is excellent influidity and productivity.

RELATED ART

Soft materials have so far been used in many cases in the fields offilms, sheets, construction materials and the like. Soft materials areused for, for example, floor materials such as cushion floors, tiles andcarpets, and polyvinyl chloride resins have so far widely been used forthe soft materials. However, the polyvinyl chloride resins generateharmful chlorine and hydrogen chloride in burning, and in additionthereto, they are likely to generate dioxins to provide environmentalproblems. Accordingly, materials substituted for polyvinyl chlorideresins and composite materials using them are desired to be developed.

Known as such materials are, for example, soft polypropylene resins.However, there have been the problems that the production processesthereof are restricted or polymers which can be produced are restricteddepending on the properties of the polymers in producing these softpolypropylene resins.

In general, used as a production process for a soft polypropylene resinis a process in which propylene is homopolymerized or copolymerized witha small amount of other olefins in a specific catalyst system by asingle stage polymerization process or a two-stage polymerizationprocess in which a propylene resin is produced in the first stagepolymerization in the same manner as described above and in whichpropylene is then random-copolymerized with other olefins. Suchprocesses are disclosed in, for example, Japanese Patent ApplicationLaid-Open No. 240069/1994 and Japanese Patent Application Laid-Open No.239935/1994. However, soft polypropylene resins have high intrinsicviscosities and therefore are short of fluidity, so that they do notnecessarily have a sufficiently high productivity in molding.

The problems described above can be solved by reducing the molecularweights of the polymers. In general, a method in which a lot of hydrogenis added in polymerization is used as a method for reducing a molecularweight of polyolefins.

However, in such production processes for soft polypropylene resins,liable to be brought about are unfavorable matters such as formation oflump of polymers, clogging of pipelines and sticking of polymers to areactor, and long-term continuous operation becomes impossible in somecases. Thus, there has been a problem on operation of an apparatus, thatis, productivity.

On the other hand, a method for modifying a propylene polymer having ahigh molecular weight by melting and kneading it in the presence of aradical-generating agent is known as a method for reducing a molecularweight of a polymer to elevate a fluidity (moldability) thereof.However, known is no method for modifying a soft propylene polymerhaving a high molecular weight by melting and kneading it in thepresence of a radical-generating agent.

Under such circumstances, an object of the present invention is toprovide a soft polypropylene resin which is useful as an alternative fora polyvinyl chloride resin in the fields of films, sheets, constructionmaterials and the like and which is excellent in fluidity andproductivity.

DISCLOSURE OF THE INVENTION

Intensive researches repeated by the present inventors in order todevelop a soft polypropylene resin which is excellent in fluidity andproductivity have resulted in finding that the above object can beachieved by a resin having a melt index falling in a specific rangewhich is obtained by melting and kneading a substantial propylenehomopolymer having a specific property or a propylene copolymercomposition in the presence of a radical-generating agent. The presentinvention has been completed based on such knowledge.

That is, the present invention provides:

-   (1) a soft polypropylene resin having a melt index (temperature:    230° C., load: 21.18N) of 1 to 10 g/10 minutes, prepared by melting    and kneading in the presence of a radical-generating agent, a    propylene resin comprising a substantial propylene homopolymer    having a boiling n-heptane-insoluble matter content of 90% by weight    or less and a intrinsic viscosity [η] of 3 to 6 deciliter/g which is    measured at 135° C. in tetralin, and-   (2) a soft polypropylene resin having a melt index (temperature:    230° C., load: 21.18N) of 1 to 10 g/10 minutes, prepared by melting    and kneading in the presence of a radical-generating agent, a    propylene resin comprising a propylene copolymer composition    comprising 10 to 95% by weight of a homogeneous part comprising a    substantial propylene homopolymer and 90 to 5% by weight of a    copolymerization part comprising a propylene-ethylene random    copolymer, wherein the homogeneous part described above has a    boiling n-heptane-insoluble matter content of 90% by weight or less    and a intrinsic viscosity [η] of 3 to 6 deciliter/g which is    measured at 135° C. in tetralin; the copolymerization part described    above comprises 10 to 60% by weight of an ethylene unit; and the    whole part has a intrinsic viscosity [η] of 3 to 6 deciliter/g which    is measured at 135° C. in tetralin.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention shall be explained below in further details.

In the soft polypropylene resin of the present invention, used as theraw material is a propylene resin comprising a substantial propylenehomopolymer or a propylene copolymer composition having the followingproperties.

The substantial propylene homopolymer used as the raw material means apropylene homopolymer or a propylene copolymer comprising 4 mole % orless of other olefin units. In the propylene copolymer described abovecomprising 4 mole % or less of other olefin units, capable of beinggiven as olefins for comonomers forming the other olefin units are, forexample, α-olefins such as ethylene, butene-1, pentene-1,4-methyl-1-pentene, hexene-1, heptene-1, octene-1, nonene-1 anddecene-1. Among them, ethylene is suited. In this propylene copolymercomprising the substantial propylene homopolymer, the boilingn-heptane-insoluble matter content is 90% by weight or less. If thiscontent exceeds 90% by weight, the resin is increased in an elasticmodulus and hardened, so that a softened polypropylene resin which is acharacteristic of the present invention can not be obtained. On theother hand, if the above insoluble matter content is too small, theabove propylene resin is likely to be short of production stability.Accordingly, the preferred boiling n-heptane-insoluble matter contentfalls in a range of 60 to 90% by weight.

The boiling n-heptane-insoluble matter content described above is avalue, which is shown by weight %, showing an extract residue obtainedafter carrying out extraction for 6 hours in boiling n-heptane by meansof a Soxhlet extract tester.

The intrinsic viscosity [η] measured at 135° C. in tetralin falls in arange of 3 to 6 deciliter/g. If this [η] is less than 3 deciliter/g,formation of lump of polymers, clogging of pipelines and sticking ofpolymers to a reactor are likely to be caused in producing the abovepropylene resin, so that the production stability is short. On the otherhand, it is difficult to produce the resin having a intrinsic viscosityexceeding 6 deciliter/g by a conventional polypropylene productionapparatus. Further, when the propylene resin having such a highintrinsic viscosity is molten and kneaded in the presence of aradical-generating agent to produce a polymer having a melt index of 1to 10 g/10 minutes, it is highly possible that fish eyes are produced ona molded article produced from such polymer.

Accordingly, the preferred intrinsic viscosity [η] falls in a range of 3to 5 deciliter/g.

On the other hand, the propylene resin comprising the propylenecopolymer composition used as the raw material comprises 10 to 95% byweight of a homogeneous part comprising a substantial propylenehomopolymer and 90 to 5% by weight of a copolymerization part comprisinga propylene-ethylene random copolymer. If the copolymerization part hasa content of exceeding 90% by weight, the soft polypropylene resinhaving a satisfactory performance is less liable to be obtained, and ifit is less than 5% by weight, the above resin is not substantiallydifferent from the propylene homopolymer described above. In a preferredcontent proportion of the homogeneous part and the copolymerizationpart, the homogeneous part falls in a range of 30 to 95% by weight, andthe copolymerization part falls in a range of 70 to 5% by weight.

In this propylene copolymer composition, the homogeneous part comprisingthe substantial propylene homopolymer described above has, because ofthe same reasons as those for the substantial propylene homopolymerdescribed above, a boiling n-heptane-insoluble matter content falling ina range of 90% by weight or less, preferably 60 to 90% by weight and aintrinsic viscosity [η] falling in a range of 3 to 6 deciliter/g,preferably 3 to 5 deciliter/g which is measured at 135° C. in tetralin.

Further, the copolymerization part described above comprising apropylene-ethylene random copolymer comprises an ethylene unit fallingin a range of 10 to 60% by weight. If this ethylene unit content is lessthan 10% by weight, the resulting soft polypropylene resin is reduced inan impact resistance, and if it exceeds 60% by weight, the resin isdeteriorated in properties because of stickiness and an increase in anadhesive component, so that it shall be difficult to continuouslyproduce the resin. Because of these reasons, the ethylene unit in theabove copolymerization part falls preferably in a range of 20 to 50% byweight.

This propylene resin comprising the propylene copolymer composition hasa intrinsic viscosity [η] of 3 to 6 deciliter/g which is measured at135° C. in tetralin. If this [η] is less than 3 deciliter/g, formationof lump of polymers, clogging of pipelines and sticking of polymers to areactor are likely to be caused in producing the above propylene resin,so that the production stability is short. On the other hand, it isdifficult to produce the resin having a intrinsic viscosity exceeding 6deciliter/g by a conventional polypropylene production apparatus.Further, when the propylene resin having such a high intrinsic viscosityis molten and kneaded in the presence of a radical-generating agent toproduce a polymer having a melt index of 1 to 10 g/10 minutes, it ishighly possible that fish eyes are produced on a molded article producedfrom such polymer.

Accordingly, the preferred intrinsic viscosity [η] falls in a range of 3to 5 deciliter/g.

This propylene resin comprising the propylene copolymer composition maybe a so-called propylene block copolymer or may be a mixture of asubstantial propylene homopolymer and a propylene-ethylene randomcopolymer.

The substantial propylene homopolymer having the properties describedabove which is used as a raw material for the soft polypropylene resinof the present invention can be produced by, for example, a gas phasesingle stage polymerization process and a slurry single stagepolymerization process. Further, the propylene copolymer composition maybe produced by, for example, a gas phase multistage polymerizationprocess and a slurry multistage polymerization process or may beprepared by blending the substantial propylene homopolymer and thepropylene-ethylene random copolymer which are separately produced.

When it is produced by, for example, a polymerization process, propylenemay be homopolymerized or may be copolymerized with ethylene in thepresence of a catalyst system comprising:

-   (W) a solid component composed of (i) a solid catalyst component    comprising magnesium, titanium, a halogen atom and an electron    donating substance and-   (ii) a crystalline polyolefin used if necessary,-   (X) an organic aluminum compound,-   (Y) an alkoxy group-containing aromatic compound represented by    Formula (I):    wherein R¹ represents an alkyl group having 1 to 20 carbon atoms; R²    represents a hydrocarbon group having 1 to 10 carbon atoms, a    hydroxyl group or a nitro group; m represents an integer of 1 to 6;    and n represents 0 or an integer of 1 to (6-m), and (Z) an electron    donating compound used if necessary.

The solid component (W) described above is composed of the solidcatalyst component of the component (i) comprising magnesium, titanium,a halogen atom and an electron donating substance and the crystallinepolyolefin of the component (ii) used if necessary. The solid catalystcomponent of the above component (i) comprises magnesium, titanium, ahalogen atom and an electron donating substance as essential componentsand can be prepared by bringing a magnesium compound, a titaniumcompound and an electron donating substance into contact. In this case,a halogen atom is contained in the magnesium compound and/or thetitanium compound in the form of a halide.

Capable of being given as the above magnesium compound are, for example,magnesium dihalides such as magnesium chloride, magnesium oxide,magnesium hydroxide, hydrotalcite, carboxylates of magnesium,alkoxymagnesiums such as diethoxymagnesium, allyloxymagnesium,alkoxymagnesium halides, allyloxymagnesium halides, alkylmagnesiums suchas ethylbutylmagnesium, alkylmagnesium halides and reaction products oforganic magnesium compounds with electron donating substances,halosilanes, alkoxysilanes, silanols and aluminum compounds. Among them,magnesium halides, alkoxymagnesiums, alkylmagnesiums and alkylmagnesiumhalides are suited. These magnesium compounds may be used alone or incombination of two or more kinds thereof.

Further, reaction products of metallic magnesium with halogens andalcohols can be used as the magnesium compound. In this case, metallicmagnesium used shall not specifically be restricted, and metallicmagnesium having an optional particle diameter, for example, granular,ribbon-shaped and powdery magnesiums can be used. The surface conditionof metallic magnesium shall not specifically be restricted as well, butmagnesium on which a coat of magnesium oxide is not formed is preferred.

Further, optional ones can be used as the alcohol, but lower alcoholshaving 1 to 6 carbon atoms are preferably used. In particular, ethanolis suited since it provides the solid catalyst component which markedlyelevates revelation of the catalyst performance. A purity and a moisturecontent of the alcohol shall not be restricted, but if alcohols having alarge moisture content are used, magnesium hydroxide is formed on ametallic magnesium surface, and therefore alcohols having a moisturecontent of 1% by weight or less, particularly 2000 ppm or less arepreferably used. The less the moisture content, the more advantageous.

The kind of halogen and/or the halogen-containing compound shall not berestricted, and any compounds can be used as the halogen-containingcompound as long as it contains a halogen atom in a molecule thereof. Inthis case, the kind of the halogen atom shall not specifically berestricted, and chlorine, bromine or iodine, particularly iodine issuitably used. Among the halogen-containing compounds,halogen-containing metal compounds are particularly preferred. A state,a form and a particle size thereof shall not specifically be restricted,and optional compounds can be used. For example, they can be used in theform of a solution prepared by dissolving them in an alcohol solvent(for example, ethanol).

A use amount of the alcohol is selected in a range of 2 to 100 moles,preferably 5 to 50 moles per mole of metallic magnesium. Too largealcohol amount tends to be less liable to provide the magnesium compoundhaving a good morphology, and if the amount is small, it is likely thatthe alcohol is not smoothly reacted with metallic magnesium.

The halogen and/or the halogen-containing compound is used in aproportion of 0.0001 mole or more, preferably 0.0005 mole or more andmore preferably 0.001 mole or more per mole of metallic magnesium interms of a halogen atom. If it is less than 0.0001 mole, thetitanium-supported amount, the catalyst activity, the stereoregularityand a morphology of the resulting polymer are reduced when the magnesiumcompound obtained is used without crushing, and crushing treating isindispensable. Accordingly, it is not preferred. Further, suitableselection of a use amount of the halogen and/or the halogen-containingcompound makes it possible to optionally control a particle diameter ofthe resulting magnesium compound.

Metallic magnesium can be reacted with the alcohol, the halogen and/orthe halogen-containing compound by a publicly known method. It is, forexample, a method in which metallic magnesium is reacted with thealcohol, the halogen and/or the halogen-containing compound underrefluxing for usually about 20 to 30 hours until hydrogen gas is notobserved to be generated to obtain the desired magnesium compound. To bespecific, when iodine is used as halogen, included are, for example, amethod in which metallic magnesium and solid iodine are added to alcoholand the mixture is then refluxed by heating, a method in which metallicmagnesium and an alcohol solution of solid iodine is dropwise added toalcohol and the mixture is then refluxed by heating and a method inwhich an alcohol solution of iodine is dropwise added to an alcoholsolution containing metallic magnesium while heating. Any method ispreferably carried out under an inert gas atmosphere of nitrogen gas orargon gas, if necessary, using an inactive organic solvent (for example,saturated hydrocarbons such as n-hexane). The respective whole amountsof metallic magnesium, the alcohol, the halogen and/or thehalogen-containing compound do not have to be added to a reactor fromthe beginning, and they may be added in a divisional manner.Particularly preferred is a method in which the whole amount of thealcohol is added from the beginning and then metallic magnesium is addedthereto in a divisional manner of several times.

Such method can prevent hydrogen gas from being temporarily produced ina large quantity and therefore is preferred very much from a safetypoint of view. Also, the above method makes it possible to make thereactor small-sized. Further, scattering and accompanying of thealcohol, the halogen and/or the halogen-containing compound caused byhydrogen gas which is temporarily produced in a large quantity can beprevented as well. The divisional frequency can be determined taking asize of the reactor into consideration, and usually 5 to 10 times issuited considering complexity of the operation. It is a matter of coursethat the reaction itself may be either a batch system or a continuoussystem. Further, it is possible as a modified method to repeat anoperation in which a small amount of metallic magnesium is first addedto the alcohol added in the whole amount from the beginning and productsformed by the reaction are removed by separating into another bath andin which a small amount of metallic magnesium is then added again.

When the magnesium compound thus obtained is used for preparing thesubsequent solid catalyst component, it may be dried and then used ormay be washed with an inactive solvent such as heptane after filteringand then used. In any case, the magnesium compound obtained is excellentin a particle form and has a narrow particle diameter distribution, andtherefore it can be used in the subsequent step without carrying out acrushing operation or a classification operation for putting a particlediameter distribution into order.

Further, a catalyst and a polymer produced using such magnesium compoundare excellent as well in a particle form and a particle diameterdistribution. This reduces problems which are likely to be caused inpolymerization, such as formation of lump of polymers, clogging ofpipelines and sticking of polymers to a reactor. Further, provided isthe advantage that handling of the polymer powder is facilitated in thesubsequent melting and kneading treatment.

The above titanium compound includes, for example, tetraalkoxytitaniumssuch as tetramethoxytitanium, tetraethoxytitanium,tetra-n-propoxytitanium, tetraisopropoxytitanium,tetra-n-butoxytitanium, tetraisobutoxytitanium,tetracyclohexyloxytitanium and tetraphenoxytitanium; titaniumtetrahalides such as titanium tetrachloride, titanium tetrabromide andtitanium tetraiodide; monoalkoxytitanium trihalides such asmethoxytitanium trichloride, ethoxytitanium trichloride, propoxytitaniumtrichloride, n-butoxytitanium trichloride and ethoxytitanium tribromide;dialkoxytitanium dihalides such as dimethoxytitanium dichloride,diethoxytitanium dichloride, dipropoxytitanium dichloride,di-n-butoxytitanium dichloride and diethoxytitanium dibromide; andtrialkoxytitanium monohalides such as trimethoxytitanium chloride,triethoxytitanium chloride, tripropoxytitanium chloride andtri-n-butoxytitanium chloride. Among them, suited is the titaniumcompounds having a higher halogen content, particularly titaniumtetrachloride. These titanium compounds may be used alone or incombination of two or more kinds thereof.

Compounds given later as the examples of the electron donating compoundof the component (Z) can be used as the electron donating substance.

The above solid catalyst component (i) can be prepared by publicly knownmethods (Japanese Patent Application Laid-Open No. 43094/1978, JapanesePatent Application Laid-Open No. 135102/1980, Japanese PatentApplication Laid-Open No. 135103/1980, Japanese Patent ApplicationLaid-Open No. 18606/1981, Japanese Patent Application Laid-Open No.166205/1981, Japanese Patent Application Laid-Open No. 63309/1982,Japanese Patent Application Laid-Open No. 190004/1982, Japanese PatentApplication Laid-Open No. 300407/1982 and Japanese Patent ApplicationLaid-Open No. 47003/1983).

The solid catalyst component (i) thus prepared has usually a compositionin which a magnesium/titanium mole ratio falls in a range of 2 to 100and a halogen/titanium mole ratio falls in a range of 5 to 100 and inwhich an electron donating substance/titanium mole ratio falls in arange of 0.1 to 10.

The crystalline polyolefin of the component (ii) used, if necessary, inpreparing the solid component (W) includes, for example, crystallinepolyolefins obtained from α-olefins having 2 to 10 carbon atoms, such aspolyethylene, polypropylene, polybutene and poly-4-methyl-1-pentene.These crystalline polyolefins can be obtained by using (1) a method(pre-polymerization method) in which olefin is pre-polymerized in thepresence of a combination of the solid catalyst component (i), theorganic aluminum compound and the electron donating compound used ifnecessary each described above, (2) a method (dispersion method) inwhich the solid catalyst component (i), the organic aluminum compoundand the electron donating compound (melting point: 100° C. or higher)used if necessary each described above are dispersed in crystallinepowder of crystalline polyethylene and polypropylene in which particlediameters are put into order and (3) a method in which the method (1)described above is combined with the method (2). Among them, preferredis the pre-polymerization method in which the catalyst component doesnot peel off from a polyolefin surface.

In the pre-polymerization method (1) described above, analuminum/titanium mole ratio is selected in a range of usually 0.1 to100, preferably 0.5 to 5. An electron donating substance/titanium moleratio falls in a range of 0 to 50, preferably 0.1 to 2.

Preferred as the pre-polymerization method (1) described above is amethod using the solid catalyst component, the organic aluminum compoundand the electron donating compound which is a stereoregularity-improvingagent, for example, an organic silicon compound among the components (Z)described later, particularly alkylalkoxysilane and arylalkoxysilane.

The pre-polymerization temperature falls preferably in a range of 1 to100° C., particularly preferably a room temperature to 50° C. andfurther preferably 35 to 40° C. The addition effects of the component(Z) and the component (Y) described later which are suitably added inpolymerization in the present invention are elevated by employing suchpre-polymerization temperature.

To be specific, it is facilitated to control a boilingn-heptane-insoluble matter content and a intrinsic viscosity of thepropylene resin before melting and kneading in the presence of theradical-generating agent. Similarly, it is facilitated to control aboiling n-heptane-insoluble matter content and a intrinsic viscosity ofthe homogeneous part in the propylene resin before melting and kneadingin the presence of the radical-generating agent. This makes it easy tocontrol a tensile elastic modulus and a Shore hardness of the softpolypropylene resin of the present invention. The pre-polymerizationpressure is preferably an atmospheric pressure to about 5 MPaG.

A proportion of the solid catalyst component (i) to the crystallinepolyolefin (ii) in the solid component (W) is selected so that a weightratio of the component (ii) to the component (i) falls in a range ofusually 0.33 to 200, preferably 0.10 to 50.

Next, a compound represented by Formula (II) can be given as the organicaluminum compound used as the component (X):AlR³ _(P)X_(3−p)  (II)wherein R³ represents an alkyl group having 1 to 20 carbon atoms or anaryl group having 6 to 20 carbon atoms; X represents a halogen atom; andp represents a number of 1 to 3. Capable of being suitably used are, forexample, trialkylaluminums such as triethylaluminum,triisopropylaluminum, triisobutylaluminum and trioctylaluminum,dialkylaluminum monohalides such as diethylaluminum monochloride,diisopropylaluminum monochloride, diisobutylaluminum monochloride anddioctylaluminum monochloride and alkylaluminum sesquihalides such asethylaluminum sesquichloride. These aluminum compounds may be used aloneor in combination of two or more kinds thereof.

In the foregoing, R³ in Formula (II) is particularly preferably an alkylgroup having 3 to 8 carbon atoms. Capable of being given as suchcompound are the compounds in which an alkyl group has 3 to 8 carbonatoms in the organic aluminum compounds described above.

Used as the component (Y) in the catalyst system suitably used forproducing the soft polypropylene resin of the present invention is thealkoxy group-containing aromatic compound represented by Formula (I):

wherein R¹ represents an alkyl group having 1 to 20 carbon atoms; R²represents a hydrocarbon group having 1 to 10 carbon atoms, a hydroxylgroup or a nitro group; m represents an integer of 1 to 6; n represents0 or an integer of 1 to (6-m).

The specific examples of this alkoxy group-containing aromatic compoundinclude monoalkoxy compounds such as m-methoxytoluene, o-methoxyphenol,m-methoxyphenol, 2-methoxy-4-methylphenol, vinylanisole,p-(1-propenyl)anisole, p-allylanisole,1,3-bis(p-methoxyphenyl)-1-pentene, 5-allyl-2-methoxyphenol,4-hydroxy-3-methoxybenzyl alcohol, methoxybenzyl alcohol, nitroanisoleand nitrophenetole; dialkoxy compounds such as o-dimethoxybenzene,m-dimethoxybenzene, p-dimethoxybenzene, 3,4-dimethoxytoluene,2,6-dimethoxyphenol and 1-allyl-3,4-dimethoxybenzene; and trialkoxycompounds such as 1,3,5-trimethoxybenzene,5-allyl-1,2,3-trimethoxybenzene, 5-allyl-1,2,4-trimethoxybenzene,1,2,3-trimethoxy-5-(1-propenyl)benzene,1,2,4-trimethoxy-5-(1-propenyl)benzene, 1,2,3-trimethoxybenzene and1,2,4-trimethoxybenzene. Among them, the dialkoxy compounds and thetrialkoxy compounds are suited. These alkoxy group-containing aromaticcompounds may be used alone or in combination of two or more kindsthereof.

Further, the electron donating compound is suitably used as thecomponent (Z) for the above catalyst. This electron donating compound isa compound containing oxygen, nitrogen, phosphorus, sulfur and silicon,and to be basic, considered is a compound having a performance forelevating stereoregularity in polymerizing propylene.

Capable of being given as such electron donating compound are, forexample, organic silicon compounds, esters, thioesters, amines, ketones,nitrites, phosphines, ethers, thioethers, acid anhydrides, acid halides,acid amides, aldehydes, organic acids and azo compounds.

It includes, for example, organic silicon compounds such asdiphenyldimethoxysilane, diphenyldiethoxysilane,dibenzyldimethoxysilane, cyclohexylmethyldimethoxysilane,tetramethoxysilane, tetraethoxysilane, tetraphenoxysilane,methyltrimethoxysilane, methyltriethoxysilane, methyltriphenoxysilane,phenyltrimethoxysilane, phenyltriethoxysilane andbenzyltrimethoxysilane; aromatic dicarboxylic acid esters such asmonomethyl phthalate, monoethyl phthalate, monopropyl phthalate,monobutyl phthalate, monoisobutyl phthalate, monoamyl phthalate,monoisoamyl phthalate, monomethyl terephthalate, monoethylterephthalate, monopropyl terephthalate, monobutyl terephthalate,monoisobutyl terephthalate, dimethyl phthalate, diethyl phthalate,dipropyl phthalate, dibutyl phthalate, diisobutyl phthalate, diamylphthalate, diisoamyl phthalate, methylethyl phthalate, methylisobutylphthalate, methylpropyl phthalate, ethylbutyl phthalate, ethylisobutylphthalate, ethylpropyl phthalate, propylisobutyl phthalate, dimethylterephthalate, diethyl terephthalate, dipropyl terephthalate, diisobutylterephthalate, methylethyl terephthalate, methylisobutyl terephthalate,methylpropyl terephthalate, ethylbutyl terephthalate, ethylisobutylterephthalate, ethylpropyl terephthalate, propylisobutyl terephthalate,dimethyl isophthalate, diethyl isophthalate, dipropyl isophthalate,diisobutyl isophthalate, methylethyl isophthalate, methylisobutylisophthalate, methylpropyl isophthalate, ethylbutyl isophthalate,ethylisobutyl isophthalate, ethylpropyl isoephthalate and propylisobutylisophthalate; monoesters such as methyl formate, ethyl formate, methylacetate, ethyl acetate, vinyl acetate, propyl acetate, octyl acetate,cyclohexyl acetate, ethyl propionate, methyl butyrate, ethyl butyrate,ethyl valerate, methyl chloroacetate, ethyl dichloroacetate, methylmethacrylate, ethyl crotonate, ethyl pivalate, dimethyl maleate, ethylcyclohexanecarboxylate, methyl benzoate, ethyl benzoate, propylbenzoate, butyl benzoate, octyl benzoate, cyclohexyl benzoate, phenylbenzoate, benzyl benzoate, methyl toluate, ethyl toluate, amyl toluate,ethyl ethylbenzoate, methyl anisate, ethyl anisate, ethylethoxybenzoate, ethyl p-butoxybenzoate, ethyl o-chlorobenzoate and ethylnaphthoate; esters such as γ-butyrolactone, δ-valerolactone, coumarin,phthalide and ethylene carbonate; organic acids such as benzoic acid andp-oxybenzoic acid; acid anhydrides such as succinic anhydride, benzoicanhydride and p-toluic anhydride; ketones such as acetone, methyl ethylketone, methyl isobutyl ketone, acetophenone, benzophenone andbenzoquinone; aldehydes such as acetoaldehyde, propionaldehyde,octylaldehyde, tolualdehyde, benzaldehyde and naphthylaldehyde; acidhalides such as acetyl chloride, acetyl bromide, propionyl chloride,butylyl chloride, isobutylyl chloride, 2-methylpropionyl chloride,valeryl chloride, isovaleryl chloride, hexanoyl chloride, methylhexanoylchloride, 2-ethylhexanoyl chloride, octanoyl chloride, decanoylchloride, undecanoyl chloride, hexadecanoyl chloride, octadecanoylchloride, benzylcarbonyl chloride, cyclohexanecarbonyl chloride, malonyldichloride, succinyl dichloride, pentanedioleyl dichloride,hexanedioleyl dichloride, cyclohexanedicarbonyl dichloride, benzoylchloride, benzoyl bromide, methylbenzoyl chloride, phthaloyl chloride,isophthaloyl chloride, terephthaloyl chloride andbenzene-1,2,4-tricarbonyl trichloride; ethers such as methyl ether,ethyl ether, isopropyl ether, n-butyl ether, isopropyl methyl ether,isopropyl ethyl ether, t-butyl ethyl ether, t-butyl n-propyl ether,t-butyl n-butyl ether, t-amyl methyl ether, t-amyl ethyl ether, amylether, tetrahydrofuran, anisole, diphenyl ether and ethylene glycolbutyl ether; acid amides such as acetic acid amide, benzoic acid amideand toluic acid amide; amines such as tributylamine,N,N′-dimethylpiperazine, tribenzylamine, aniline, pyridine, pyrrolineand tetramethylethylenediamine; nitrites such as acetonitrile,benzonitrile and tolunitrile; and azo compounds in which a sterichindrance substituent is bonded to an azo bond, such as2,2′-azobis(2-methylpropane), 2,2′-azobis(2-ethylpropane) and2,2′-azobis(2-methylpentane).

Among them, preferred are the organic silicon compounds, the esters, theketones, the ethers, the thioethers, the acid anhydrides and the acidhalides, and particularly suited are the organic silicon compounds suchas diphenyldimethoxysilane, cyclohexylmethyldimethoxysilane andphenyltriethyoxysilane, the aromatic dicarboxylic acid diesters such asdiethyl phthalate, di-n-butyl phthalate and diisobutyl phthalate and thealkyl esters of aromatic monocarboxylic acids such as benzoic acid,p-methoxybenzoic acid, p-ethoxybenzoic acid and toluic acid. Theseelectron-donating compounds may be used alone or in combination of twoor more kinds thereof.

In respect to the use amounts of the respective components in thecatalyst system, the solid component (W) is used in such an amount asfalling in a range of usually 0.0005 to 1 mole per liter of a reactionvolume in terms of a titanium atom. The organic aluminum compound (X) isused in such an amount that a mole ratio of aluminum/titanium atoms isusually 1 to 3000, preferably 40 to 800, and if this amount deviatesfrom the range described above, the catalyst activity is likely tobecome unsatisfactory. Further, the alkoxy group-containing compound (Y)is used in such a proportion that a mole ratio thereof to a titaniumatom contained in the solid component (W) is usually 0.01 to 500,preferably 1 to 300, and if this ratio is less than 0.01, the resultingpolymer is likely to be reduced in physical properties. On the otherhand, if it exceeds 500, the catalyst activity is likely to becomeunsatisfactory.

In the present invention, when producing the substantial propylenehomopolymer, it can be produced by homopolymerizing propylene orcopolymerizing propylene with 4 mole % or less of olefin in the presenceof the catalyst system described above by a single-stage polymerizationmethod.

On the other hand, when producing the propylene copolymer composition,it can be produced by a two-stage polymerization method in which asubstantial propylene homopolymer is produced in the first stagepolymerization in the same manner as described above and in whichpropylene is then random-copolymerized with ethylene in the second stagepolymerization, or as described above, the substantial propylenehomopolymer and the propylene-ethylene random copolymer may beseparately produced and then blended.

The polymerization method shall not specifically be restricted, and usedare slurry polymerization, gas phase polymerization, bulkpolymerization, solution polymerization and suspension polymerization.

When the polymerization is carried out by gas phase polymerization, thepolymerization pressure is suitably selected in a range of usually 1 to5 MPa, preferably 2 to 3 MPa, and the polymerization temperature issuitably selected in a range of usually 40 to 90° C., preferably 60 to75° C. A molecular weight of the polymer can be controlled by a publiclyknown method, for example, by controlling a hydrogen concentration in apolymerization vessel. The polymerization time is suitably selected in arange of 5 minutes to 10 hours.

In the polymerization, the respective components constituting thecatalyst system, that is, the components (W) to (Z) are blended in theprescribed proportion and brought into contact, and then the rawmaterial monomer may be immediately introduced to start polymerizationor the mixture is ripened for 0.2 to 3 hours after bringing intocontact, and then the raw material monomer may be introduced. Further,these catalyst components can be suspended in an inactive solvent orolefin of the raw material monomer and then fed.

After-treatment after polymerization can be carried out by aconventional method. That is, in a gas phase polymerization method,nitrogen flow may be allowed to pass through a polymer powder dischargedfrom a polymerization vessel after polymerization in order to removeunreacted monomers contained therein. Further, the polymer may bepelletized, if necessary, by means of an extruding machine, and in thiscase, a small amount of water and alcohol can be added in order tocompletely deactivate the catalyst. In a bulk polymerization method,unreacted monomers are completely removed from a polymer discharged froma polymerization vessel after polymerization, and then the polymer canbe pelletized.

In the present invention, the substantial propylene homopolymer thusobtained or the propylene resin comprising the propylene copolymercomposition is molten and kneaded in the presence of theradical-generating agent, whereby obtained is a soft polypropylene resinhaving a melt index (MI) falling in a range of 1 to 10 g/10 minuteswhich is measured on the conditions of a temperature of 230° C. and aload of 21.18 N.

In this melting and kneading in the presence of the radical-generatingagent, the substantial propylene homopolymer described above and/or thepropylene resin (hereinafter referred to as a treated propylene resin)comprising the propylene copolymer composition are preferably blendedwith an antioxidant (B), water (C) and a neutralizing agent (D) togetherwith the radical-generating agent (A), and the mixture is preferablymolten and kneaded.

The radical-generating agent of the component (A) described above haspreferably a decomposition temperature which is not too low in order toobtain a homogeneous soft polypropylene resin, and the temperature forobtaining a half value period of 10 hours is usually 70° C. or higher,preferably 100° C. or higher. Capable of being given as such compoundare, for example, organic peroxides such as benzoyl peroxide, t-butylperbenzoate, t-butyl peracetate, t-butyl peroxyisopropylcarbonate,2,5-di-methyl-2,5-di(benzoylperoxy)hexane,2,5-di-methyl-2,5-di(benzoylperoxy)hexyne-3, t-butyl-di-peradipate,t-butylperoxy-3,5,5-trimethoxyhexanoate, methyl-ethyl ketone peroxide,cyclohexanone peroxide, di-t-butyl peroxide, dicumyl peroxide,2,5-di-methyl-2,5-di(t-butylperoxy)hexane,2,5-di-methyl-2,5-di(t-butylperoxy)hexyne-3,1,3-bis(t-butylperoxyisopropyl)benzene, t-butylcumyl peroxide,1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane,1,1-bis(t-butylperoxy)cyclohexane, 2,2-bis(t-butylperoxy)butane,p-menthane hydroperoxide, di-isopropylbenzene hydroperoxide, cumenehydroperoxide, t-butyl hydroperoxide, p-cymene hydroperoxide,1,1,3,3-tetramethylbutyl hydroperoxide,2,5-di-methyl-2,5-di(hydroperoxy)hexane, trimethylsilyl-cumyl peroxide,2,5-di-methyl-2,5-bis(trimethylsilylperoxy)hexane,2,5-di-methyl-2,5-bis(trimethylsilylperoxy)hexyne-3 and1,3-bis(trimethylsilylperoxyisopropyl)benzene. Among them, particularlypreferred are 2,5-di-methyl-2,5-di(t-butylperoxy)hexane,2,5-di-methyl-2,5-di(t-butylperoxy)hexyne-3 and1,3-bis(t-butylperoxyisopropyl)benzene. These radical-generating agentsmay be used alone or in combination of two or more kinds thereof. A useamount thereof is selected in a range of usually 0.001 to 0.5 part byweight, preferably 0.01 to 0.2 part by weight per 100 parts by weight ofthe treated propylene resin.

Phenol antioxidants and phosphorus antioxidants are preferred as theantioxidant of the component (B), and particularly suited is acombination of a phenol antioxidant (B-1) and a phosphorus antioxidant(B-2).

The phenol antioxidant of the component (B-1) includes, for example,6-di-t-butyl-p-cresol, 2-t-butyl-4,6-dimethylphenol,2,6-di-t-butyl-4-ethylphenol, 2,6-di-t-butyl-4-n-butylphenol,2,6-diisobutyl-4-n-butylphenol, 2,6-di-cyclopentyl-4-methylphenol,2-(α-methylcyclohexyl)-4,6-dimethylphenol,2,6-di-octadecyl-4-methylphenol, 2,4,6-tri-cyclohexylphenol,2,6-di-t-butyl-4-methoxymethylphenol,n-octadecyl-β-(4′-hydroxy-3′,5′-di-t-butylphenyl)propionate,2,6-di-t-butyl-4-methoxylphenol, 2,5-di-t-butyl-hydroquinone,2,5-di-t-amyl-hydroquinone, 2,2′-thio-bis-(6-t-butyl-4-methylphenol),2,2′-thio-bis-(4-octylphenol), 2,2′-thio-bis-(6-t-butyl-3-methylphenol),4,4′-thio-bis-(6-t-butyl-2-methylphenol),4,4′-thio-bis-(6-t-butyl-3-methylphenol),4,4′-thio-bis-(2,6-di-t-butylphenol),2,2′-methylene-bis-(6-t-butyl-4-methylphenol),2,2′-methylene-bis-(6-t-butyl-4-ethylphenol),2,2′-methylene-bis-[4-methyl-6-(α-methylcyclohexyl) -phenol],2,2′-methylene-bis-(4-methyl-6-cyclohexylphenol),2,2′-methylene-bis-(6-nonyl-4-methylphenol),2,2′-methylene-bis-[6-(α-methylbenzyl)-4-nonylphenol],2,2′-methylene-bis-[6-(α,α-dimethylbenzyl)-4-nonylphenol],2,2′-methylene-bis-(4,6-di-t-butylphenol),2,2′-ethylidene-bis(4,6-di-t-butylphenol),2,2′-ethylidene-bis(6-t-butyl-4-isobutylphenol),4,4′-methylene-bis(2,6-di-t-butylphenol),4,4′-methylene-bis(6-t-butyl-2-methylphenol),4,4′-butylidene-bis(6-t-butyl-2-methylphenol),4,4′-butylidene-bis(6-t-butyl-3-methylphenol),4,4′-butylidene-bis(2,6-di-t-butylphenol),4,4′-butylidene-bis(3,6-di-t-butylphenol),1,1-bis(5-t-butyl-4-hydroxy-2-methylphenyl-butane,2,6-di(3-t-butyl-5-methyl-2-hydroxybenzyl)-4-methylphenol,calcium-bis[o-ethyl-(3,5-di-t-butyl-4-hydroxybenzyl) phosphonate],2-t-butyl-6-(3-t-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenylacrylate, 2-t-butyl-6-[3-t-butyl-2-hydroxy-5-methyl (α-methylbenzyl)]-4-methylphenyl acrylate, 2,4-di-t-butyl-6-[3,5-di-t-butyl-2-hydroxy(α-methylbenzyl)]phenyl acrylate,2,4-di-t-amyl-6-[3,5-di-t-amyl-2-hydroxy(α-methylbenzyl)]-phenylacrylate, tocopherol, 2,6-diphenyl-4-octadecyloxyphenol,2,4-bis(n-octylthio)-6-(4-hydroxy-3,5-di-t-butylanilino)-1,3,5-triazine,2,4,6-tris(2′-hydroxy-4′-octoxyphenyl)-1,3,5-triazine,2,4,6-tris[3-(3′,5′-di-t-butyl-4′-hydroxyphenyl)-ethyl]-1,3,5-triazine,2,4,6-tris(3′,5′-di-t-butyl-4′-hydroxybenzylthio)-1,3,5-triazine,1,3,5-tris(3′,5′-di-t-butyl-4′-hydroxybenzylacetyl)-hexahydro-1,3,5-triazine,1,3,5-tris(4-t-butyl-3-hydroxy-2,6-dimethylbenzyl)-1,3,5-triazine-2,4,6-(1H,2H, 5H)trione, 1,1,3-tris(5-t-butyl-4-hydroxy-2-methylphenyl)-butane,triethylene glycolbis[3-(3-t-butyl-5-methyl-4-hydroxyphenyl)propionate], 1,6-hexanediolbis[3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate],N,N′-bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyl]-hexamethylenediamine,3,5-di-t-butyl-4-hydroxybenzylphosphonate diethyl ester,2,2-thio-diethylene-bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate],bis[3,3-bis(4′-hydroxy-3′-t-butylphenyl)butyric acid] ethylene glycolester, bis[3,3-bis(4′-hydroxy-3′-methyl-5′-t-butylphenyl)-butyric acid]ethylene glycol ester,bis[3,3-bis(4′-hydroxy-3′,5′-di-t-butylphenyl)butyric acid] ethyleneglycol ester, bis[3,3-bis(4′-hydroxy-3′-t-butylphenyl)butyric acid]2,2-bis(hydroxyethoxyphenyl)propane ester,bis[3,3-bis(4′-hydroxy-3′-methyl-5′-t-butylphenyl)butyricacid]-2,2-bis(hydroxyethoxyphenyl)propane ester,bis[3,3-bis(4′-hydroxy-3′,5′-di-t-butylphenyl)butyric acid]2,2-bis(hydroxyethoxyphenyl)propane ester,bis[2-(3′-t-butyl-2′-hydroxy-5′-methylbenzyl)-6-t-butyl-4-methylphenyl]terephthalate,3,9-bis(3,5-di-t-butyl-4-hydroxyphenyl)-2,4,8,10-tetraoxaspiro[5,5]-undecane,3,9-bis[1,1-dimethyl-2-(3,5-di-t-butyl-4-hydroxyphenyl)ethyl]-2,4,8,10-tetraoxaspiro[5,5]-undecane,3,9-bis[1,1-dimethyl-2-{β-(3-t-butyl-4-hydroxy-5methylphenyl)propionyloxy}ethyl]-2,4,8,10-tetraozaspiro[5,5]undecane,3,9-bis[1,1-dimethyl-2-{β-(3,5-di-t-butyl-4-hydroxyphenyl)propionyloxy}-ethyl]2,4,8,10-tetraoxaspiro[5,5]undecane,3,9-bis[1,1-dimethyl-2-{β-(3,5-diphenyl-4-hydroxyphenyl)propionyloxy}ethyl]-2,4,8,10-tetraoxaspiro[5,5]undecane,3,9-bis[1,1-dimethyl-2-{β-(3,5-dicyclohexyl-4-hydroxyphenyl)propionyloxy}-ethyl]-2,4,8,10-tetraoxaspiro[5,5]undecane,1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene,tris(3,5-di-t-butyl-4-hydroxybenzyl)isocyanurate,tris(4-t-butyl-3-hydroxy-2,6-dimethylbenzyl)isocyanurate,tris[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyloxyethyl]isocyanurate,2,2-bis-[4-[2-(3-methyl-5-butyl-4-hydroxyphenyl-propionyloxy)ethoxy]phenyl]propane,2,2-bis-[4-[2-(3,5-di-t-butyl-4-hydroxyphenylpropionyloxy)-ethoxy]phenyl]propane,tetrakis[methylene-3-(3′-methyl-5′-t-butyl-4′-hydroxyphenyl)propionate]methaneandtetrakis[methylene-3-(3′,5-di-t-butyl-4′-hydroxyphenyl)propionate]methane.These phenol antioxidants may be used alone or in combination of two ormore kinds thereof.

On the other hand, the phosphorus antioxidant of the component (B-2)includes, for example, trioctyl phosphite, trilauryl phosphite,tristridecyl phosphite, trisisodecyl phosphite, phenyldiisooctylphosphite, phenyldiisodecyl phosphite, phenyldi(tridecyl) phosphite,diphenylisooctyl phosphite, diphenylisodecyl phosphite, diphenyltridecylphosphite, triphenyl phosphite, tris(nonylphenyl) phosphite,tris(2,4-di-t-butylphenyl) phosphite, tris(butoxyethyl) phosphite,tetratridecyl-4,4′-butylidenebis(3-methyl-6-t-butylphenol) diphosphite,4,4′-isopropylidene-diphenolalkyl phosphite (provided that alkyl has 12to 15 carbon atoms),4,4′-isopropylidenebis(2-t-butylphenol).di(nonylphenyl) phosphite,tris(biphenyl) phosphite,tetra(tridecyl)-1,1,3-tris(2-methyl-5-t-butyl-4-hydroxyphenyl)butanediphosphite, tris(3,5-di-t-butyl-4-hydroxyphenyl) phosphite,hydrogenated 4,4′-isopropylidenediphenol polyphosphite,bis(octylphenyl).bis[4,4′-butylidenebis(3-methyl-6-t-butylphenol)].1,6-hexanedioldiphosphite, hexatridecyl-1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenol)phosphite, tris[4,4′-isopropylidenebis(2-t-butylphenol)] phosphite,tris(1,3-distearoyloxyisopropyl) phosphite,9,10-dihydro-9-phosphaphenanthrene-10-oxide,tetrakis(2,4-di-t-butylphenyl)-4,4′-biphenylenediphosphonate,distearylpentaerythritol diphosphite, di(nonylphenyl)pentaerythritoldiphosphite, phenyl.4,4′-isopropylidenediphenol-pentaerythritoldiphosphite, bis(2,4-di-t-butylphenyl)pentaerythritol diphosphite,bis(2,6-di-t-butyl-4-methylphenyl) pentaerythritol diphosphite andphenyl bisphenol-A-pentaerythritol diphosphite.

Among them, preferred are tris(2,4-di-t-butylphenyl) phosphite,tris(nonylphenyl) phosphite andtetrakis(2,4-di-t-butylphenyl)-4,4′-biphenylene diphosphonite. Thesephosphorus antioxidants may be used alone or in combination of two ormore kinds thereof.

In the present invention, in respect to the antioxidants of thecomponent (B), the phenol antioxidant of the component (B-1) isadvantageously blended in a proportion of usually 0.01 to 1 part byweight, preferably 0.02 to 0.5 part by weight per 100 parts by weight ofthe treated propylene resin, and the phosphorus antioxidant of thecomponent (B-2) is advantageously blended in a proportion of usually0.01 to 3 parts by weight, preferably 0.05 to 2 parts by weight. If theblending amounts of the phenol antioxidant and the phosphorusantioxidant are smaller than the ranges described above, it is likelythat the thermal oxidation degradation-preventing effect is notsufficiently exhibited. On the other hand, if the amounts are largerthan the ranges described above, the effects thereof are not elevated inproportion to the amounts blended, and it is rather disadvantageous froman economical point of view.

Water of the component (C) is advisably blended in a proportion ofusually 0.01 to 1 part by weight, preferably 0.05 to 0.5 part by weightper 100 parts by weight of the treated propylene resin. If this blendingamount is less than 0.01 part by weight, it is likely that thecoloring-preventing effect is not sufficiently exhibited. On the otherhand, if it exceeds 1 part by weight, the effect thereof is not elevatedin proportion to the amount blended, and foaming is rather notablycaused. Accordingly, it is not practical.

Further, the neutralizing agent of the component (D) shall notspecifically be restricted and includes conventionally known compounds,for example, hydrotalcite and calcium stearate. A blending amount ofthis neutralizing agent is selected in a range of usually 0.05 to 5 partby weight, preferably 0.1 to 2 parts by weight per 100 parts by weightof the treated propylene resin.

A kneading method in producing the soft polypropylene resin of thepresent invention shall not specifically be restricted, and variousmethods can be used according to the situations. A method shown below ispractically used because of easiness in operation.

First, the component (A), the component (B), the component (C) and thecomponent (D) each described above are added respectively to thesubstantial propylene homopolymer and/or the propylene resin comprisingthe propylene copolymer composition each obtained in the mannerdescribed above in the prescribed proportions, and suitably addedthereto are, if necessary, various other additives which are usuallyadded to propylene resins, to be specific, light stabilizers,transparency-providing agents, nucleating agents, lubricants,anti-static agents, anti-blocking agents, heavy metal-deactivatingagents, fillers, pigments, flame retardants and mold release agents.They are compounded by means of a Henschel mixer, a super mixer, aribbon blender, a Banbury mixer and a tumbler and mixed at such atemperature that the radical-generating agent is not decomposed. Then,this mixture is molten and kneaded at a melt-kneading temperature of 150to 350° C., preferably 180 to 270° C. by means of various melt-kneadingapparatuses such as a single shaft extruding machine, a double shaftextruding machine, a brablender and a roll, preferably a melt-kneadingapparatus having a deaerating zone, and then it is pelletized, wherebythe desired soft polypropylene resin of the present invention isobtained. Water may be added to the above mixture immediately before orin a melting zone of the melt-kneading apparatus.

The desired soft polypropylene resin thus obtained has to have a meltindex (MI, measured at a temperature of 230° C. and a load of 21.18N)falling in a range of 1 to 10 g/10 minutes which is measured accordingto JIS K7210. If this MI is less than 1 g/10 minutes, the resin isinferior in fluidity in molding, so that the molding cycle is delayed,and a production efficiency of the molded article is reduced. On theother hand, if MI exceeds 10 g/10 minutes, a lot of fish eyes areproduced on the molded article such as a film and a sheet. MI issuitably 1 to 7 g/10 minutes.

Further, in the soft polypropylene resin of the present invention, amelt peak temperature (Tm) measured by means of a differential scanningcalorimeter (DSC) is preferably 150° C. or higher. If Tm is lower than150° C., the sufficiently high heat resistance can not be obtained. ThisTm falls usually in a range of 150 to 165° C. On the other hand, themelt enthalpy (ΔH) measured by means of DSC is preferably 100 J/g orless. If ΔH exceeds 100 J/g, the flexibility is damaged, and the objectof the present invention is not achieved in a certain case. This ΔHfalls usually in a range of 20 to 100 J/g, preferably 30 to 80 J/g.

Further, the tensile elastic modulus (according to JIS K7113) ispreferably 800 MPa or less. It is preferably 200 MPa or less. If it isless than 200 MPa, the polymer has no problem on flexibility. However,the production stability is likely to be reduced, and a problem onproductivity is likely to be caused.

The Shore hardness (D scale, according to JIS K7215) is preferably 80 orless. It is preferably 40 or more. If it is less than 40, the moldedarticle is liable to be scratched on a surface thereof.

Next, the present invention shall more specifically be explained withreference to examples, but the present invention shall by no means berestricted by these examples.

The physical properties of the soft polypropylene resins obtained in therespective examples were determined by methods shown below.

(1) Met Index (MI)

Measured on the conditions of a temperature of 230° C. and a load of21.18N according to JIS K7210.

(2) Melting Point (Tm) and (3) Melt Enthalpy (ΔH)

The melting point and the melt enthalpy were determined by DSCmeasurement. That is, a differential scanning calorimeter (DSC-7,manufactured by Perkin Elmer Co., Ltd.) was used to melt 10 mg of asample at 230° C. for 3 minutes under nitrogen atmosphere, and then thetemperature was lowered down to 0° C. at a rate of 10° C./minute andmaintained the temperature at 0° C. for 3 minutes. Further, thetemperature was elevated at a rate of 10° C./minute to obtain a meltendothermic curve, wherein a peak top in a maximum peak in the meltendothermic curve was designated as the melting point (Tm), and a meltendothermic amount was designated as the melt enthalpy (ΔH) (J/g)

(4) Tensile Elastic Modulus

Measured by a tensile test using a No. 2 dumbbell according to JISK7113.

(5) Shore Hardness (D Scale)

Measured according to JIS K7215

EXAMPLE 1

(1) Preparation of Magnesium Compound

A stainless steel-made catalyst reactor was sufficiently substitutedwith nitrogen gas and then charged with 25 kg of ethanol (moisturecontent: 100 ppm), 1.6 g of iodine and 16 kg of metallic magnesium, andthey were reacted under a heating condition while stirring untilhydrogen gas was not observed to be generated from the system under arefluxing condition to obtain a solid reaction product. The reactionsolution containing this solid reaction product was dried under reducedpressure to obtain a magnesium compound.

(2) Preparation of Solid Catalyst Component

A stainless steel-made catalyst reactor having a content volume of 500liter which was sufficiently substituted with nitrogen gas was chargedwith 16 kg of the magnesium compound obtained in (1) described above, 80liter of refined heptane, 2.4 liter of silicon tetrachloride and 2.3liter of diethyl phthalate. Titanium tetrachloride 77 liter was addedthereto while maintaining the system at 90° C. and stirring to carry outreaction at 110° C. for 2 hours, and then the solid component wasseparated and washed with refined heptane of 80° C. Further, 122 literof titanium tetrachloride was added thereto to carry out reaction at110° C. for 2 hours, and then the solid matter was sufficiently washedwith refined heptane to obtain a solid catalyst component.

(3) Pre-Polymerization

A stainless steel-made polymerization reactor having a content volume of80 liter which was sufficiently substituted with nitrogen gas wascharged with 4 kg of the solid catalyst component obtained in (2)described above, 40 liter of refined heptane, 1.6 mole oftriethylaluminum and 0.4 mole of cyclohexylmethyldimethoxysilane, andthen propylene was continuously fed for 2 hours while maintaining thesystem at 40° C. and stirring to carry out pre-polymerization almost atan atmospheric pressure. After stopping feeding propylene, the systemwas maintained at a temperature of 40° C. for 30 minutes. Then, thesolid matter was washed with refined heptane to obtain apre-polymerization catalyst.

(4) Polymerization

A continuous production apparatus was fed with 1.30 kg/hr of thepre-polymerization catalyst obtained in (3) described above and chargedwith 52 mole of triisobutylaluminum, 8 mole ofcyclohexylmethyldimethoxysilane and 1.6 mole of1-allyl-3,4-dimethoxybenzene each per mole of a titanium atom containedin the above pre-polymerization catalyst, and further a propylenemonomer was fed to carry out continuous gas phase polymerization at atemperature of 70° C., a pressure of 2.8 MPa.G and an average residencetime of one hour, whereby a propylene homopolymer was obtained.

This propylene homopolymer had a boiling n-heptane-insoluble mattercontent of 88% by weight and a intrinsic viscosity [η] of 4.8deciliter/g which was measured at 135° C. in tetralin.

(5) Dissolution and Pelletization

Added to 100 parts by weight of the propylene homopolymer obtained in(4) described above were 0.02 part by weight of1,3,5-tris(4-t-butyl-3-hydroxy-2,6-dimethylbenzyl)-1,3,5triazine-2,4,6-(1H,2H, 5H)trione, 0.05 part by weight oftetrakis(2,4-di-t-butylphenyl)-4,4′-biphenylene phosphinate, 0.05 partby weight of tris(2,4-di-t-butylphenyl) phosphite, 0.075 part by weightof Mg_(4.5)Al₂(OH)₁₃CO_(3.)3.5H₂O, 0.075 part by weight of calciumstearate and 0.017 part by weight of1,3-bis(t-butylperoxyisopropyl)benzene, and then 0.35 part by weight ofwater was further added thereto. The mixture was molten and kneaded sothat the resin temperature was 220° C. and then pelletized to obtain apelletized soft polypropylene resin. The physical properties of thisresin are shown in Table 1.

EXAMPLE 2

A soft polypropylene resin was obtained in the same manner as in Example1(5), except that an addition amount of1,3-bis(t-butylperoxyisopropyl)-benzene was changed from 0.017 part byweight to 0.014 part by weight in Example 1 (5). The physical propertiesof this resin are shown in Table 1.

Comparative Example 1

The same operations as in Example 1 (1) to (3) were carried out toobtain a pre-polymerization catalyst. Next, propylene was fed to bepolymerized in the same manner as in Example 1 (4), except that hydrogenwas introduced at a rate of 50 liter/hr in polymerization in Example 1(4), but clogging of the pipelines and stirring fluctuation were heavy,and operation was impossible, so that a soft polypropylene resin couldnot be obtained.

EXAMPLE 3

A soft polypropylene resin was obtained in the same manner as in Example1, except that in Example 1 (4), a propylene monomer was homopolymerizedin the reaction of the first stage, and then propylene wasrandom-copolymerized with ethylene in the reaction of the second stageto obtain a propylene block copolymer.

In the operation described above, two reactors were used to produce thepropylene-ethylene block copolymer. A propylene homopolymer dischargedfrom the reactor of the first stage was deaerated before introduced intothe reactor of the second stage and then introduced into the reactor ofthe second stage which was controlled to 50° C. A monomer gas having acomposition ratio of ethylene/propylene=2/5 (mole ratio) was introducedinto the reactor of the second stage to copolymerize ethylene andpropylene at a pressure of 1.5 MPa·G, a temperature of 50° C. and anaverage residence time of one hour.

The propylene-ethylene block copolymer thus obtained was dissolved andpelletized in the same manner as in Example 1 (5) to obtain a softpolypropylene resin. The physical properties of this resin are shown inTable 1.

In the propylene-ethylene block copolymer described above, a homogeneouspart comprising the propylene homopolymer had a content of 62% byweight, and a copolymerization part comprising the propylene-ethylenerandom copolymer had a content of 38% by weight. The homogeneous parthad a boiling n-heptane-insoluble matter content of 68% by weight and aintrinsic viscosity [η] of 4.2 deciliter/g which was measured at 135° C.in tetralin. On the other hand, the copolymerization part had anethylene unit content of 37.6% by weight. Further, this the propyleneblock copolymer had a intrinsic viscosity [η] of 4.3 deciliter/g whichwas measured at 135° C. in tetralin.

TABLE 1 Example 1 2 3 Melt index [MI] (g/10 minutes) 2.6 1.6 2.3 Meltingpoint [Tm] (° C.) 161.3 156.4 158.4 Melt enthalpy [ΔH] (J/g) 75.6 74.443.9 Tensile elastic modulus (MPa) 773 662 241 Shore hardness (D scale)69 69 49

INDUSTRIAL APPLICABILITY

According to the present invention, a substantial propylene homopolymeror a propylene copolymer composition each having specific properties ismolten and kneaded in the presence of a radical-generating agent,whereby capable of being obtained is a soft polypropylene resin which isuseful as an alternative for a polyvinyl chloride resin in the fields offilms, sheets, construction materials and the like and which isexcellent in fluidity.

1. A soft polypropylene resin having a melt index at a temperature of230° C. and a load of 21.18N of 1 to 10 g/10 minutes, obtained bymelting and kneading, in the presence of a radical-generating agent, apropylene resin composition comprising a substantial propylenehomopolymer having a boiling n-heptane-insoluble matter content of 60 to90% by weight and an intrinsic viscosity of 3 to 6 deciliter/g measuredat 135° C. in tetralin.
 2. A soft polypropylene resin having a meltindex at a temperature of 230° C. and a load of 21.18N of 1 to 10 g/10minutes, obtained by melting and kneading, in the presence of aradical-generating agent, a propylene resin composition comprising apropylene copolymer composition comprising 10 to 95% by weight of ahomogeneous part comprising a substantial propylene homopolymer and 90to 5% by weight of a copolymerization part comprising apropylene-ethylene random copolymer, herein the homogeneous part has aboiling n-heptane-insoluble matter content of 60 to 90% by weight and aintrinsic viscosity of 3 to 6 deciliter/g measured at 135° C. intetralin; the copolymerization part comprises 10 to 60% by weight ofethylene; and the propylene resin composition has an a intrinsicviscosity of 3 to 6 deciliter/g measured at 135° C. tetralin.
 3. Thesoft polypropylene resin as described in claim 1, wherein the propyleneresin composition is first blended with a radical-generating agent (A),an antioxidant (B), water (C) and a neutralizing agent (D) to form ablended mixture, and the blended mixture is melted and kneaded at atemperature of 150 to 350° C.
 4. The soft polypropylene resin asdescribed in claim 3, wherein the antioxidant of the component (B)comprises a phenol antioxidant (B-1) and a phosphorus antioxidant (B-2).5. The soft polypropylene resin as described in claim 4, obtained byblending 100 parts by weight of the propylene resin with 0.001 to 0.5part by weight of the component (A), 0.01 to 1 part by weight of thecomponent (B-1), 0.01 to 3 parts by weight of the component (B-2), 0.01to 1 part by weight of the component (C) and 0.05 to 5 parts by weightof the component (D) to form the blended mixture, and melting andkneading the blended mixture.
 6. The soft polypropylene resin asdescribed in claim 2, wherein the propylene resin composition is firstblended with a radical-generating agent (A), an antioxidant (B), water(C) and a neutralizing agent (D), to form a blended mixture and theblended mixture is melted and kneaded at a temperature of 150 to 350° C.7. A soft polypropylene resin having a melt index at a temperature of230° C. and a load of 21.18N of 1 to 10 g/10 minutes, obtained bymelting and kneading, in the presence of a radical-generating agent, apropylene resin composition comprising a substantial propylenehomopolymer having a boiling n-heptane-insoluble matter content of 60 to90% by weight and an intrinsic viscosity of 3 to 6 deciliter/g measuredat 135° C. in tetralin, wherein the propylene homopolymer is obtained byhomopolymerizing propylene in the absence of hydrogen and in thepresence of a catalyst comprising solid catalyst comprising magnesium,titanium, a halogen and an electron donating substance; triisobutylaluminum; and an alkoxy group-containing aromatic compound.
 8. The softpolypropylene resin as described in claim 7, wherein the propylene resincomposition is first blended with a radical-generating agent (A), anantioxidant (B), water (C) and a neutralizing agent (D), to form ablended mixture and the blended mixture is melted and kneaded at atemperature of 150 to 350° C.
 9. The soft polypropylene resin asdescribed in claim 8, wherein the antioxidant of the component (B)comprises a phenol antioxidant (B-1) and a phosphorus antioxidant (B-2).10. The soft polypropylene resin as described in claim 8, obtained byblending 100 parts by weight of the propylene resin with 0.001 to 0.5part by weight of the component (A), 0.01 to 1 part by weight of thecomponent (B-1), 0.01 to 3 parts by weight of the component (B-2), 0.01to 1 part by weight of the component (C) and 0.05 to 5 parts by weightof the component (D) to form a blended mixture, and melting and kneadingthe blended mixture.
 11. A soft polypropylene resin having a melt indexat a temperature of 230° C. and a load of 21.18N of 1 to 10 g/10minutes, obtained by melting and kneading, in the presence of aradical-generating agent, a propylene resin composition comprising apropylene copolymer composition comprising 10 to 95% by weight of ahomogeneous part comprising a substantial propylene homopolymer and 90to 5% by weight of a copolymerization part comprising apropylene-ethylene random copolymer, wherein the homogeneous part has aboiling n-heptane-insoluble matter content of 60 to 90% by weight and aintrinsic viscosity of 3 to 6 deciliter/g measured at 135° C. intetralin; the copolymerization part comprises 10 to 60% by weight ofethylene unit; and the propylene copolymer composition has an intrinsicviscosity of 3 to 6 deciliter/g measured at 135° C. in tetralin, whereinthe propylene copolymer is obtained by copolymerizing ethylene andpropylene in the absence of hydrogen and in the presence of a catalystsystem comprising a solid catalyst comprising magnesium, titanium, ahalogen and an electron donating substance; triisobutyl aluminum; and analkoxy group-containing aromatic compound.
 12. The soft polypropyleneresin as described in claim 11, wherein the propylene resin compositionis first blended with a radical-generating agent (A), an antioxidant(B), water (C) and a neutralizing agent (D), to form a blended mixtureand the blended mixture is melted and kneaded at a temperature of 150 to350° C.
 13. The soft polypropylene resin as described in claim 12,wherein the antioxidant of the component (B) comprises a phenolantioxidant (B-1) and a phosphorus antioxidant (B-2).
 14. The softpolypropylene resin as described in claim 13, obtained by blending 100parts by weight of the propylene resin with 0.001 to 0.5 part by weightof the component (A), 0.01 to 1 part by weight of the component (B-1),0.01 to 3 parts by weight of the component (B-2), 0.01 to 1 part byweight of the component (C) and 0.05 to 5 parts by weight of thecomponent (D) to form the blended mixture, and melting and kneading theblended mixture.
 15. A soft polypropylene resin having a melt index at atemperature of 230° C. and a load of 21.18N of 1 to 10 g/10 minutes,obtained by melting and kneading, in the presence of aradical-generating agent, a propylene resin composition comprising asubstantial propylene homopolymer having a boiling n-heptane-insolublematter content of 60 to 90% by weight and an intrinsic viscosity of 3 to6 deciliter/g measured at 135° C. in tetralin, wherein the propylenehomopolymer is obtained by homopolymerizing propylene in the absence ofhydrogen and in the presence of a catalyst system comprising a solidcatalyst comprising magnesium, titanium, a halogen and an electrondonating substance; triisobutyl aluminum; and an alkoxy group-containingaromatic compound; wherein the catalyst system comprises a compositionobtained by prepolymerizing propylene in the presence of the solidcatalyst and an organic aluminum compound.
 16. The soft polypropyleneresin of claim 15, wherein the solid catalyst is prepolymerized beforethe propylene is homopolymerized.
 17. The soft polypropylene resin ofclaim 15, wherein the catalyst system is obtained by prepolymerizingpropylene in the presence of the solid catalyst, an organic aluminumcompound and an electron donating compound.
 18. A soft polypropyleneresin having a melt index at a temperature of 230° C. and a load of21.18N of 1 to 10 g/10 minutes, obtained by melting and kneading, in thepresence of a radical-generating agent, a propylene resin compositioncomprising a propylene copolymer composition comprising 10 to 95% byweight of a homogeneous part comprising a substantial propylenehomopolymer and 90 to 5% by weight of a copolymerization part comprisinga propylene-ethylene random copolymer, wherein the homogeneous part hasa boiling n-heptane-insoluble matter content of 60 to 90% by weight andan intrinsic viscosity of 3 to 6 deciliter/g measured at 135° C. intetralin; the copolymerization part comprises 10 to 60% by weight ofethylene units; and the propylene copolymer composition has an intrinsicviscosity of 3 to 6 deciliter/g measured at 135° C. in tetralin, whereinthe propylene copolymer is obtained by copolymerizing ethylene andpropylene in the absence of hydrogen and in the presence of a catalystsystem comprising a solid catalyst comprising magnesium, titanium, ahalogen and an electron donating substance; triisobutyl aluminum; and analkoxy group-containing aromatic compound; wherein the catalyst systemis obtained by prepolymerizing propylene in the presence of the solidcatalyst and an organic aluminum compound.
 19. The soft polypropyleneresin of claim 18, wherein the catalyst system is obtained byprepolymerizing propylene in the presence of the solid catalyst, anorganic aluminum compound and an electron donating compound.
 20. Thesoft polypropylene resin of claim 18, wherein the prepolymerization ofthe catalyst system with propylene is carried out before the propyleneis copolymerized with ethylene.